The AM Forum

For a relay controlling an inductive load, does a bi-directional transorb make any sense as an alternative to the usual capacitor in series with a resistor snubber? This is 120 VAC,  not RF, a relay controlling a motor and a second relay controlling a solenoid.

On one hand they can conduct huge currents and happily eat up the big transients, on the other hand, the 'on' voltage is pretty high, so they may allow some sparking. That's a super question. I'm not sure I am qualified to answer however Littelfuse has this useful article about selecting them:
http://www.littelfuse.com/products/tvs-diodes.aspx
The PDF helpfully comparing transient suppression methods referenced in the article is attached. I could not find one directly comparing a TVS to a snubber.

I use to use the 1.5KE160C's as AC input clamping devices and they worked quite well.  They are very fast and don't have the same wear out mechanism that MOV's have.  MOV's in time, will reduce their clamping voltage until they come into the steady state voltage region that they are protecting and then that's it for the life of a MOV.  Transorbs are more like fast zeners and do not have this slopping cure after multiple hits.  The restriction is the amount of energy during an transient condition they can handle. 

Here is a data sheet showing the unidirectional and bi-directional device offerings.  Generally the "C" in the part number indicates a bi-directional device which you would use for AC clamping applications. 

Joe, W3GMS     

Thanks

Joslyn makes the best transient suppressors ever.

I have some on our 480V service.  A big surge came along and they blew the fuses on the 12.7kV mains, but no damage to any of our stuff here at home. :o

Pretty tough stuff...reportedly an unlimited lifespan, too ;).

Find bargain prices on eBay for 'em.

73DG